Quote:
Originally Posted by Spookyer
Something to do with "inertial moment"
|
You can balance a telescope with a given counterweight mass at a given offset distance, or a smaller mass at a proportionately larger distance (eg half the mass at twice the distance). The further apart the balanced masses are, the greater the Moment of Inertia:
I = m r^2
(Eg for the case of half the mass / twice the distance, you get double the Moment of Inertia.)
The bigger the Moment of Inertia, the more the telescope will tend to continue to move whenever it is disturbed; think of two pendulums of equal length, one with a small bob and the other with a large bob. They both swing with the same period, but the heavier bob will take longer to overcome friction and stop swinging. Hence it makes sense to use a larger mass at a smaller offset, all other things being equal.